TIM GANNON PHOTO | A coiled extension cord plugged into a space heater caused this Flanders home to be destroyed by fire Monday.

The fire that destroyed an elderly man’s home in Flanders Monday morning was caused by a 100-foot long extension cord that was plugged into a space heater and coiled in cardboard box with clothes piled on top of it, according to Southampton Town Fire Marshal John Rankin.

The 73-year-old sole occupant of the Pricilla Avenue home was rescued by a neighbor who pounded on his door and pulled him out of the burning house shortly before the fire intensified.

“Extension cords are meant for temporary use, and you should extend them out to their full length, because that will dissipate the heat,” Mr. Rankin said.

The coiled extension cord heated in the box and eventually set both the cardboard box and the clothing on fire, said Mr. Rankin, who said a nearby mattress then went up in flames, too.

Joe Marshall, who lives just a few doors down, was driving past the house on the way to his mother’s house when he saw smoke coming out the window.

“As soon as he got him out, the whole house lit up, which indicates that the entirety of the house probably flashed over,” Mr. Rankin said. “Basically, this means that everything in the house catches fire at the same time, almost like an explosion.”

Mr. Marshall reported seeing overhead electrical wires leading into the house begin to explode.

The homeowner, Richard Morrison, was taken to Peconic Bay Medical Center for treatment of smoke inhalation and second-degree burns on his back, caused by burning debris from the house falling on him, Mr. Rankin said.